Vascular endothelial cells are known to contain at least three RGD-dependent integrins, including the vitronectin receptors αvβ3 or αvβ5 as well as the collagen types I and IV receptors αvβ1 and α2β1, the laminin receptors α6β1 and α3β1, and the fibronectin receptor α5β1 (Davis et al., 1993, J. Cell. Biochem. 51, 206). The smooth muscle cell is known to contain at least six RGD-dependent integrins, including αvβ3 and αvβ5.
Inhibition of cell adhesion in vitro using monoclonal antibodies immunospecific for various integrin α or β subunits have implicated the vitronectin receptor αvβ3 in cell adhesion processes of a variety of cell types including microvascular endothelial cells (Davis et al., 1993, J. Cell. Biol. 51, 206).
Integrins are a class of cellular receptors known to bind extracellular matrix proteins, and mediate cell-extracellular matrix and cell-cell interactions, referred generally to as cell adhesion events. The integrin receptors constitute a family of proteins with shared structural characteristics of non-covalenty associated heterodimeric glycoprotein complexes formed of α and β subunits. The vitronectin receptor, named for its original characteristic of preferential binding to vitronectin, is now known to refer to four different integrins, designated αvβ1, αvβ3, αvβ5 and αvβ8. αvβ1 binds fibronectin and vitronectin. αvβ3 binds a large variety of ligands, including fibrin, fibrinogen, laminin, thrombospondin, vitronectin and von Willebrand's factor. αvβ5 binds vitronectin. It is clear that there are different integrins with different biological functions as well as different integrins and subunits having shared biological specificity and function. One important recognition site in a ligand for many integrins is the Arg-Gly-Asp (RGD) tripeptide sequence. RGD is found in all of the ligands identified above for the vitronectin receptor integrins. The molecular basis of RGD recognition by αvβ3 has been identified (Xiong et al., 2001) This RGD recognition site can be mimicked by linear and cyclic (poly)peptides that contain the RGD sequence. Such RGD peptides are known to be inhibitors or antagonists, respectively, of integrin function. It is important to note, however, that depending upon the sequence and structure of the RGD peptide, the specificity of the inhibition can be altered to target specific integrins. Various RGD polypeptides of varying integrin specificity have been described, for example, by Cheresh, et al., 1989, Cell 58, 945, Aumailley et al., 1991, FEBS Letts. 291, 50, and in numerous patent applications and patents (e.g. U.S. Pat. Nos. 4,517,686, 4,578,079, 4,589,881, 4,614,517, 4,661,111, 4,792,525; EP 0770 622).
The generation of new blood vessels, or angiogenesis, plays a key role in the growth of malignant disease and this has generated much interest in developing agents that inhibit angiogenesis.
Nevertheless, although various combination therapies utilizing potential angiogenesis inhibitors are under investigation, in clinical trials and on the market, the outcome of these therapies are not fruitful enough. Therefore, there still exists a need in the art to develop further combinations which can show increased efficacy and reduced side-effects.
It is known today that tumor vasculature is different from vasculature of healthy tissue. The vasculature is characteristic for the tumor and distinct from the stable, dormant vasculature of healthy tissue. It is often characterized by an increased expression and priming of specific cell adhesion molecules of the alpha-v-integrin series especially αvβ3 and αvβ5. When activated these integrins enhance the cellular response to growth factors that drive angiogenesis, for example VEGFA and FGF2: VEGFA was originally termed vascular permeability factor, and it acts via the SRC kinase pathway to increase local vascular permeability. VEGRF2, when activated, increases the activity of αvβ3 integrin.
Further, solid tumors depend on an induced and cooped vasculature from the host to develop. This vasculature has unusual molecular properties that distinguish it from the normal host vasculature: it tends to be activated, i.e. progressing through cell cycle under the influence of tumor-derived factors like VEGFs, FGFs and others, and expresses endothelial activation markers like ICAM, VCAM and alpha-v-series Integrins, e.g. αvβ3 and αvβ5, in a ligand competent state. It has a defective extracellular matrix, and is classically described as leaky. It is notable that tumors often resist therapies systemically applied via the blood stream, due to abnormal nature of tumor vasculature.
The metastatic process is a multistep event and represents the most dreadful aspect of cancer. At the moment of diagnosis, cancers are frequently far advanced in their natural history, and the presence of metastases is a common event. In fact, approximately 30% of patients have detectable metastases at the moment of clinical diagnosis and a further 30% of patients have occult metastases. Metastases can be disseminated and they can infest different organs at the same time, or localize to a specific organ. In the case of localized disease, surgery is the treatment of choice; however recurrence and prognosis depend on many criteria such as: resectability, patient's clinical situation, and number of metastases.
After resection, recurrence is common, suggesting that micrometastatic foci are present at the moment of diagnosis. Systemic chemotherapy is an ideal setting but only few patients are cured by it, and in the majority systemic chemotherapy fails. Many physiological barriers and pharmacokinetic parameters contribute to decrease its efficacy.
Liver, lungs and lymph nodes are filtration organs and therefore inclined to metastasization. The poor chemosensitivity of metastases, peculiarly those of colorectal origin has forced many researchers to use methods for increasing the time and the concentration of drugs. The need for decreasing or limiting the side effects for this important and delicate organ led to the development of the technique of liver isolation for perfusion of antineoplastic agents. (K. R. Aigner, Isolated liver perfusion. In: Morris D L, McArdle C S, Onik G M, eds. Hepatic Metastases. Oxford: Butterworth Heinemann, 1996. 101-107). Since 1981, modifications and technical improvements have been continuously introduced. Liver metastases may be of different origin and their chemosensitivity may vary according to the histological type and their response in presence of heat.
There still exists a growing need in the art in order to develop new therapeutics trategies for treating cancer, especially metastases systemically. The object of the present invention therefore was to develop such a new strategy. It should be applicable to systemic treatment, and it should lower the dose and/or increase the efficiency of the cancer therapeutical agents to be applied. A further object was to normalize tumor vasculature to increase delivery of systemic therapeutics of tumor, i.e. to reset the tumor vasculature to the functionality of the vasculature of non-tumor tissue.
Thus, it is a preferred objective of the instant invention to provide a more effective, better tolerated treatment for humans, especially human cancer patients suffering from breast cancer and/or bone metastases, preferably breast cancer and/or bone metastases independent from their origin, thus preferably leading to enhanced overal survival (OS), progression-free survival (PFS), quality of life (QOL) and/or increased median survival.